The Humminbird Fish Finder 688ci HD XD Combo is a unit that combines chartplotting functions with extreme depth fish finding capabilities. The head unit of this Humminbird is pretty much similar to the other units of the 600 series. It has a 5-inch diagonal screen, brilliant color and backlit, 480H x 640V pixel resolution. Has a power output of 1,000 Watts (RMS) / 8,000 Watts (PTP), being capable of scanning depths up to 3,000 feet.
It has Dual Beam Plus Sonar, and Xtreme Depth (that’s what the XD stands for) sonar, making available 3 distinctive operability modes: 20° coverage / 200 kHz, 60° coverage / 83 kHz, and 74° coverage / 50 kHz, for the extreme depth mode. The standard transducer included by the box is a Transom XNT 9 DB 74 T., with a Quick-Disconnect mounting kit. In-Dash mounting kits also work for this fish finder, but they’re optional. It does not have Side Imaging and Down Imaging, and does not support 360 Imaging.
This unit is also equipped with precision GPS, and the UniMap cartography package, which covers the contiguous U.S. coastline and inland waters at 30m / pixel. It can store up to 2,500 waypoints, 45 routes and 50 tracks (20,000 points each). The 688ci HD XD Combo is compatible with Lakemaster and Navionics Gold/HotMaps and can support an optional SD card for a cartography upgrade. Radar2 and NMEA2000 are also not available for this unit.